JP2002290417A - Radio lan system adaptable to noise environment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radio LAN system adaptable to noise environment, which sets an optimal modulation/demodulation method for a noise environment to switch over a data transmission rate automatically, without changing a signal modulation speed. SOLUTION: A means (20) that changes the data transmission rate by combination of IQ biorthogonal codes and QAM(quadrature amplitude modulation) without changing the signal modulation speed is provided in the radio LAN system adaptable to noise environment equipped with a modem, which selects automatically the data transmission rate according to the condition of the noise environment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise environment adaptive wireless LAN system provided with a modem for automatically selecting a data transmission speed according to a noise environment, and more particularly to measuring a noise to obtain a data transmission speed according to the noise environment. The present invention relates to a noisy environment adaptive wireless LAN system having a modem that changes the communication environment.

[0002]

2. Description of the Related Art A conventional wireless LAN operates well in a good communication environment without noise, but the communication path is blocked by noise near roads, factories, and other noise sources, and stable communication is performed. There are drawbacks that cannot be guaranteed.

In a network communication system proposed in Japanese Patent Application Laid-Open No. 11-284688, for example, modulation systems such as VSB for terrestrial signals, QSPK for QAM satellite signals for wired signals, and DMT for telephone terrestrial lines are used. Is prepared in a general-purpose modem, and the modulation type on both the transmitting side and the receiving side is controlled in accordance with the channel noise so that the demodulation type can be changed to the corresponding type.

[0004] However, this proposal does not specify the detection location of the noise environment and the method of transmitting the detected noise characteristic.
In particular, no specific proposal has been made for a data transmission method in a wireless LAN in a limited frequency band according to a noise environment.

The present applicant detects a noise situation during wireless LAN communication, selects a data transmission rate in accordance with the noise environment, and makes the transmitting and receiving apparatus optimally modulate and demodulate by software processing to stabilize. The present invention proposes a wireless LAN system adapted to a noise environment that guarantees secure communication.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems in the prior art by setting a modulation and demodulation method most suitable for a noise environment without changing a signal modulation speed. The purpose of the present invention is to provide a wireless LAN system adapted to a noise environment, which can automatically switch the data transmission speed.

[0007]

SUMMARY OF THE INVENTION A noise environment adaptive wireless LAN system according to the present invention is a noise environment adaptive wireless LAN system having a modem for automatically selecting a data transmission rate according to a noise environment. And Q
Means are provided for changing the data transmission rate without changing the modulation rate by a combination of AM modulation. In the above,
The transmitting side selects and modulates the data transmission rate from the combination of the IQ bi-orthogonal code and the QAM modulation, and transmits the data. The receiving side demodulates the data by a demodulation method that matches the modulation method.

The means for changing the data transmission speed includes a digital signal processor (DSP), a storage device and an A / D
It is composed of a converter, a D / A converter, and a PC interface, and has a function of detecting a noise environment from a signal received through the A / D converter and a function of selecting and demodulating the received signal from a plurality of demodulation methods. It is preferable to have a function and a function of selecting a transmission signal to be transmitted from a plurality of modulation schemes, modulating the transmission signal, and transmitting the modulated signal via a D / A converter. In the above, the storage device is a program in which the DSP detects a noise characteristic from the received signal, a program that detects header information of the received signal, a program that demodulates data of the received signal, a program that determines header information of the transmitted signal, A program for modulating data is externally downloaded and stored.

[0009] It is preferable that the transmission signal is composed of a packet modulated by a header modulated by a fixed modulation scheme and data modulated by an arbitrary modulation scheme. In the above description, the header of the transmission packet is unified with a predetermined fixed modulation method, and the data portion takes into account the noise environment of the transmitting side (own station) and the noise environment of the receiving side (other station) and the data transmission rate and modulation. Determine the method.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a wireless LAN system adapted to a noise environment according to the present invention will be described with reference to the drawings. FIG. 1 shows a configuration of an embodiment of a transmitting and receiving terminal device used in a wireless LAN system adapted to a noise environment according to the present invention.

In FIG. 1, a noise environment adaptive wireless LA
The transmission / reception terminal device 1 of the N system includes an antenna 10, a transmission / reception switch 11, an RF power amplifier 12, and an up-converter 1.
3; an RF receiver 12; a down-converter 15; a DSP modem 20 for selecting an optimum data transmission rate in accordance with a noise environment to perform modulation / demodulation; and a personal computer (hereinafter abbreviated as a personal computer) 30. .

The antenna 10 has a function of transmitting and receiving to and from an external station. The antenna 10 is connected to a transmission / reception switch 11 by a line 10L. The transmission side of the transmission / reception switch 11 is connected to an RF power amplifier 12 by a line 11LA and disconnected freely. The receiving side of the transmission / reception switch 11 is connected to the RF receiver 14 by a line 11LB and is freely connected. The transmission / reception switch 11 except for when transmitting,
Normally, it is set so as to be connected to the RF receiver 14.

The RF receiver 14 has a function of receiving a received signal and transmitting the received signal to the down converter 15 via a line 14L.

The down-converter 15 is an RF receiver 14
Has a frequency conversion function of lowering the analog signal output to a low frequency that can be processed by the DSP modem 20, and the output side is connected to the DSP modem 20 by a line 15L.

The DSP modem 20 includes an A / D converter 22
, A D / A converter 21, a digital signal processor (hereinafter abbreviated as DSP) 23, and a storage device (hereinafter, referred to as DSP).
Recorded as memory. ) 24 and a PC interface 25, each of which is communicated by an internal bus 29.

The DSP 23 has a function of analyzing a noise environment around the own station from a received signal, a function of demodulating the signal, and a function of modulating a transmission signal. These functions are realized by a program stored in the DSP 23 and the memory 24. And is communicated with other devices in the DSP 20 via a bus 29.

The memory 24 includes a program for the DSP 23 to detect noise characteristics from the received signal, a program for detecting header information of the received signal, a program for demodulating data of the received signal, a program for determining header information of the transmitted signal, and a program for determining header information of the transmitted signal. A program or the like for modulating the above data is downloaded from the personal computer 30 when the system 1 is started up, so as to respond to the operation of the DPS 23. In addition,
If the storage capacity of the memory 24 is large, all or a part of each of the programs may be built in advance.

The PC interface 25 has a function of communicating between the DSP 23 and the personal computer 30.
The SP 23 is connected to a bus 29, and the personal computer 30 is connected to a line 25L.

The A / D converter 22 is a down converter 1
5 is provided with a function of converting an analog signal, which is the output of 5, into a digital signal, and is connected to the DSP 23 by a bus 29.

The D / A converter 21 has a function of converting a digital transmission signal modulated by the DSP 23 into an analog signal, and is connected to the up-converter 13 by a line 13L.

The up-converter 13 is a D / A converter 2
It has a frequency conversion function of increasing the frequency of a relatively low frequency signal from 1 to an RF wave, and is connected to the RF power amplifier 12 via an output line 12L.

The RF power amplifier 12 has a function of amplifying and transmitting an RF wave from the up-converter 13 to an output covering a transmission area.

The personal computer 30 has a function of summarizing the contents of transmission and reception and a function of controlling the entire DSP modem 20, and incorporates various modulation and demodulation programs used by the DSP 23. It has a function of downloading necessary programs to the memory 24. The personal computer 30 and the DSP modem 23
L and the PC via the PC interface 25.

FIG. 2 shows an example of the format of a packet transmitted by the present apparatus.

The packet Pk is formed of a header Hd and data D. The header Hd indicates the synchronization system H1, the start H2, the address H3, the noise information H4, the modulation information H5, etc. in bits, for example, indicating the modulation system. The modulation information uses 3 bits to identify the modulation scheme of FIG. 3 described later. The modulation method of the header Hd is determined so that one of the modulation methods shown in FIG. 3 is fixedly used. The data D is configured to be modulated in accordance with the modulation method specified by the modulation information H5 in the header Hd.

FIG. 3 shows the modulation schemes which are incorporated in the personal computer 30 and downloaded to the memory 24 as needed. FIG. 3 shows, as variables, QAM, IQ, and QPSK modulation schemes using a modulation signal as a variable in the left column, and shows the characteristics of each modulation scheme in the right column. Here, k is the number of input data bits, n is a channel symbol, rc is a bit increment coefficient, rcRs is a bit rate (the bit rate Rs in the table is calculated based on 2400 symbols / sec), and dmin 2 is Shortest distance between signals,
nd indicates the maximum number of shortest distance signals, and Es indicates signal energy. In FIG. 3, if the 64-IQ modulation is used, the minimum bit rate 900 in the table is obtained. In the present embodiment, normally, 64-IQ modulation is applied to the modulation of the header Hd.

The processing steps of a program operating in the modem 20 will be described with reference to FIG. This program is
For example, when the power of the modem 20 and the personal computer 30 is turned on, the data is downloaded from the personal computer 30 to the memory 24 in the modem 20 via the line 25L.

When a receiving instruction is given from the personal computer 30 via the line 25L, a receiving process starting from a receiving start step iS1 is started.

At step iS2, the down converter 15
Is converted into digital data by the A / D converter 22, and the converted data is temporarily stored in the memory 24.

In step iS3, the A / D data stored in the memory 24 by the DSP 23 is demodulated by a predetermined demodulation method, for example, the data transmission speed 64 shown in FIG.
-Demodulate by IQ demodulation. In the above description, a method of storing and demodulating a predetermined number of data in the memory 24 and demodulating the data collectively is described. However, a method of demodulating for each sample data may be used. If the demodulation of the Heb Hd succeeds by this demodulation, the process proceeds to the next step iS5.

In step iS5, by analyzing the header Hd detected in step iS3, the noise information of the transmitting station, the modulation method of the data D following the header Hd, and the like are determined. Then, the contents are stored in the memory 24.

In step iS6, based on the result of step iS5, data D below the header Hd is selected from dMA, dMB,... Corresponding to the modulation method shown in FIG. .

In step iS7, the received information packet Pk demodulated as described above is transferred to the personal computer 30 via the PC interface 35. The above steps iS1 to iS7 are steps of a program process for demodulating received information. The following steps are steps of a program process for transmitting information.

At step iS4, the received signal wave is analyzed to analyze the noise disturbing the transmitted wave sent to the own station. This analysis operation is performed as a background job between the demodulation operations, and the analysis result is stored in the memory 24. This analysis is performed at regular time intervals to constantly update the analysis result.

When a transmission instruction is given from the personal computer 30 via the line 25L, a transmission process starting from step oS1 is started.

In step oS2, the transmission data is transferred from the personal computer 30 to the memory 24.

In step oS3, the optimum modulation method is selected from FIG. 3 by examining the noise environment analysis result of the own station and the noise environment of the partner station, which are analyzed in the reception processing and stored in the memory 24.

In step oS4, based on the result of step oS3, the data D below the header Hd of the packet Pk to be transmitted is MA, MA corresponding to the modulation method shown in FIG.
The modulation method is selected from among MB.
The noise information and the modulation information of the transmission data are written in the header Hd of the packet Pk. Note that the modulation method of the header Hd is the same as the modulation method applied to the header Hd of the received packet Pk, and is modulated by a method that is previously unified in the present system.

In step oS5, the transmission data modulated as described above is converted by the D / A converter 21 into analog data. The analog signal is output from the up converter 1
3, transmitted from the antenna 10 via the RF power amplifier 12 and the transmission / reception switch 11.

[0040]

The effects of the present invention are listed below. (1) According to the noise environment adaptive wireless LAN system of the present invention, on the receiving side, demodulation is performed by the demodulation method on the basis of information on the modulation method that modulates data below the header written in the header of the transmission packet. The transmitting side examines the noise information of the transmitting station and the noise environment around the own station, and modulates the noise environment with a modulation method that allows the largest data rate for the noise environment at that time. As a result, the modulation method is automatically changed so as to select the optimum transmission speed according to the noise environment, so that stable information transmission can be performed. (2) Since the data transmission speed is changed without changing the signal modulation speed, the communication system can be operated within a predetermined frequency band. (3) Also, high-efficiency transmission using signal power effectively can be performed, and signal power per unit frequency can be suppressed to a minimum, so that influence on other devices can be minimized.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a terminal device used in a wireless LAN system adapted to a noise environment according to the present invention.

FIG. 2 is a diagram showing a format of a packet used in the wireless LAN system.

FIG. 3 is a table showing characteristics of a modulation scheme used in the wireless LAN system.

FIG. 4 is an operation procedure diagram for explaining the configuration of FIG. 1;

[Explanation of symbols]

 D: Data Hd: Header Pk: Packet 1: Terminal device 10: Antenna 11: Transmission / reception switch 12: RF power amplifier 13: Up converter 14: RF receiver 15:・ Down converter 20 ・ ・ DSP modem 21 ・ ・ D / A converter 22 ・ ・ A / D converter 23 ・ ・ DSP 24 ・ ・ Memory 25 ・ ・ PC interface 30 ・ ・ PC

Continued on the front page F term (reference) 5K004 AA08 JD02 JE00 JG00 5K033 AA01 AA05 CC01 DB09 EA02 5K034 AA05 AA15 DD01 EE03 HH01 HH02 KK28 MM08 SS01 5K067 AA05 BB21 CC08 EE02 HH23

Claims (3)

[Claims] 1. A noise environment adaptive wireless LAN having a modem for automatically selecting a data transmission rate according to a noise environment.
A noise environment adaptive wireless LAN system, comprising: means for changing a data transmission rate without changing a modulation rate by a combination of an IQ code and a QAM modulation. 2. The data transmission rate changing means includes a digital signal processor (DSP), a storage device, and an A / D converter.
A D converter, a D / A converter, and a PC interface, a function of detecting a noise environment from a signal received through the A / D converter, and demodulation by selecting the received signal from a plurality of demodulation methods. 2. The noise environment adaptive wireless LAN system according to claim 1, wherein said wireless LAN system has a function of causing a transmission signal to be transmitted to be selected from a plurality of modulation schemes, modulating the signal, and transmitting the modulated signal via a D / A converter. 3. The noise environment adaptive wireless LAN system according to claim 2, wherein the transmission signal comprises a packet formed by a header modulated by a fixed modulation scheme and data modulated by an arbitrary modulation scheme.